Many modern gas turbine engines, especially those used for propulsion, are configured to include relatively long rotors and relatively small turbine tip clearances. This combination of features, upon engine shutdown, can cause what is known as a “bowed rotor event” if the engine is not spooled down slowly.
One solution that has been postulated to alleviate a bowed rotor event is to pulse width modulate the solenoid-actuated starter air valve (SAV) as part of engine startup sequence, to thereby supply air to the air turbine starter at a pressure that is lower than during engine light-off speed. Doing so may require, in some instances, over 27 million cycles of operation of the solenoid actuator for lifetime of a component. Unfortunately, presently known solenoids are not designed to operate against very high vibration, high pressure and with the required number of operational cycles, or for higher than MTBF (mean time before failure) of greater than 60,000 engine hours.
Hence, there is a need for a high cycle, high vibration capable solenoid that will enable single on/off valve actuation or PWM valve modulation while maintaining suitable operational integrity throughout the needed number of operational cycles. The present invention addresses at least these needs.